Still stricter environmental and safety regulations do not allow free burial of the waste. Controlled land filling may be the preferred option, depending on the composition of the buried material. It is desirable to convert the waste to a less harmful product, and possibly to reduce its volume, while preferably recovering some of materials. Hundreds of thousands tons of sulfur-containing waste accumulates from chemical and other industries around the world every year. A significant source of sulfur waste are filter cakes from the massive production of sulfuric acid, resulting from molten sulfur filtered through media based on diatomaceous earth and lime. Controlled burial is necessary in order to prevent the formation and spreading of sulfur compounds, which is cost demanding. When exposed to oxygen, sulfur may undergo slow oxidation creating acidic problematic environment, while anaerobic bacterial reactions may occur in the deeper layers of the landfill which will produce smelly and toxic sulfides. It is therefore an object of this invention to provide a method of converting sulfur-containing waste to spent precoat material which could be economically buried by landfilling. This invention also aims at recovering sulfur from said waste. U.S. Pat. No. 2,508,292 relates to sulfur vaporization and purification, comprising a complex system of hot ceramic particles circulating through the reactor. US 2009/0242379 relates to the recovery and purification of sulfur, comprising hot steam directly contacting sulfur deposits and melting them. The existing systems are too complicated, and do not enable to convert sulfur-rich waste to environmentally material for landfilling or to provide a pure recovered sulfur product in a cost-effective industrial manner. It is another object of this invention to separate sulfur from spent precoat materials in solid waste, without introducing further substance, while recovering sulfur in a practical industrial process, in a cost-effective manner.
It is another object of this invention to provide an environmentally friendly industrial process for recovering sulfur from sulfur-containing waste in high yields, while converting the waste to low volume, sulfur-free material which may be landfilled, while employing an economical process and complying with the valid land filling regulations.
Other objects and advantages of present invention will appear as description proceeds.